1. Field of the Invention
The present invention relates to a frame rate converting technique for converting the number of image frames used, for example, for an image display apparatus.
2. Description of the Related Art
In the image display apparatus, as a technique for displaying a moving image after having converted a frame rate (frame frequency) of image signal transmitted through a television broadcast into a desired frame rate, for example, a technique described in JP-A-2001-111968 is known.
In the related art described above, when increasing the frame rate of the image signal as a conversion process, a process to repeat the same frame a plurality of times is performed. For example, when doubling the frame rate of an image signal having a frame row of (F1, F2 . . . ), a process to repeat each frame two times each, such as (F1, F1, F2, F2 . . . ) is performed. Therefore, in the image signal after conversion, the position of an object which moves within the display is the same between the repeated two frames. Therefore, in the related art, it is difficult to achieve smooth movement of the moving image after the frame rate conversion.
The above described problem is obvious when a 2-3 pulldowned interlace image signal is displayed by 60 frames per second. The 2-3 pulldown system image signal is converted into the image signal of 24 frames per second once by reverse pulldown process in the image display apparatus, and then is converted into an image signal of 60 frames per second by repeating the same frame image in the order of two frames, three frames, two frames, three frames . . . . Therefore, since the image after conversion is switched in its image contents every 2/60, 3/60 seconds, even when it is an image in which an object moves in the screen at a constant velocity, the amount of movement of the object per unit time is no longer constant after conversion. Also, since the time period in which the same frame is displayed is increased, achievement of smooth movement is further difficult.